Sulfonation process



July 15, 195s c. F. w. GEBELEI'N ETAL SULFONATION PROCESS Filed Sept. 20, 1955 tmlntthw INEI Charles F. W. Gebelein Charles A. Reass Inventors By @4MM Attorney stamt sutroNsrroN rnoenss Charles iF. W. Gebelein, Butler, Pa., and Charles A. Reuss,

Wakeeld, Mass., assigner-s to Esso Research and Enginecring Company, a corporation of Delaware Appiication eptember 20, 1955, Serial No. 535,348

Claims. (Cl. 260--505) This invention relates to an improved process for preparing sulfonic acids and oil-soluble sulfonates. By this improved process, a sulfonation product of selected molecular weight and excellent color is obtained. rlhe sulfonates obtained by this proces find use as lubricants, emulsifying agents and as lubricating oil additives.

yln brief compass, oil-soluble sulfonates are prepared according to this invention by reacting synthetic alkyl aryl hydrocarbon feed stocks diluted with a prepared inert hydrocarbon diluent oil, with reactive amounts of a sulfonating agent. The sulfonic acids obtained by the sulfonation are then extracted, neutralized and concentrated in a conventional manner to obtain oil-soluble sulfonates of exceptional purity.

A synthetic alkyl aryl hydrocarbon feed stock, as used in the specification and claims, includes only mono, di, and tri-alkyl substituted one-ring and two-ring aromatic hydrocarbons as the reactive ingredients which when sulfonated form oil-soluble sulfonic acids. The feed stock may include some inert or nonreactive oils. The synthetic feed stock has a sulfonatable hydrocarbon content over 6() vol. percent. ln the case `of mono nuclear aromatic hydrocarbons the molecular weight of the sum of the alkyl groups exceeds 240. The molecular Weight of the sum of the alkyl groups in the two-ring hydrocarbons is greater than 180. rl`he feed stock is substantially free of aromatic hydrocarbons containing more than 2 aromatic nuclei. Active ingredients in the feed stock may comprise for example such materials as polypropyl benzene and toluene, triamyl naphthalene and mono and polyalkylated naphthalene.

Synthetic `feed stock of the alkyl aryl type can be made from selected kerosene 'fractions contaning a high amount of straight chain parafns having about l2 carbon atoms. The selected fraction can iirst be chlorinated to form keryl chloride and then can be alkylated with benzene using aluminum chloride as a catalyst to form keryl benzene, keryl meaning derived from the selected kerosene fraction. Other sources of alkyl groups can be used such as propylene tetramer and butylene trimer.

Synthetic alkyl aryl hydrocarbon feed stocks as described above have been made available for sulfonation but generally cannot be sulfonated directly because of processing diiculties brought about by the high concentration of sulfonatable hydrocarbons present in the feed. lt is desired, however, to use selected feed stocks when a product of high purity or of select molecular weight is sought.

The maximum concentration of sulfonates typically obtained in conventional White oil sulfonation processes is limited to l5 to 18 wt. percent at best. ln the present invention, a sulfonic acid concentrate is produced that contains 25 to 35% sulfonic acid.

The present invention by a novel process permits sulfonation of synthetic feed stocks while obtaining high yields of a product of exceptional purity and of excellent color having a molecular Weight typical of the molecular Weight of the synthetic feed stock. The product is free tent from pepper sludge and contaminating oil soluble sulfonic acids that would be derived from an untreated diluent. In the preferred application of this invention feed stocks are used that result in sulfonic acid products having molecular Weights in t-he ranges of 400 to 900, depending on the molecular Weight of the synthetic feed stock used. The feed is selected so as to obtain a product having a narrow molecular weight range and a high degree of purity.

To permit sulfonation `of such a synthetic feed stock, a specially prepared inert hydrocarbon diluent is used in the practice of this invention. By prepared inert hydrocarbon diluent oil, `as used in the specification and claims, it is meant to include only petroleum oils boiling in a range Within the limits of 200 to 800 F., such as naphthas, gas oils, and White oils, either of naphthenic or parafnic origin, which have been highly acid treated with concentrated sulfuric acid or the like to remove substantially completely -all sulfonatable hydrocarbons from the oil. This diluent contains less than 2.0%, preferably less than 0.5%, sulfonatable hydrocarbon. The amount of sulfonatable hydrocarbons in the oil may be determined by the Unsulfonated vResidue Test (ASTM Designation: D483-52T).

At this time, a diluent oil that is predominately pararlinic is preferred Iand it is preferred that the diluent have a viscosity in the range of 50 to 350 SSU at 100 F., more especially to 130 SSU at 100 F. The amount of diluent used in the practice `of this invention is sufficient to reduce `the viscosity of the feed stock to below 450 SSU at F. The viscosity of the diluent is selected with respect to the feed stock such `that the amount of diluent used does not reduce the amount of sulfonatable hydrocarbons present in the mixture to below 30 volume percent.

By the term sulfonating agent, it is meant to include conventional sulfonating materials including 98% sulfurie acid, oleum and liquid or gaseous S03. Generally a sufficient amount of sulfonating agent is used to supply 2.0 to 7.0 moles of S03 per mole of sulfonatable hydrocarbon. When 20% to 30% oleum is employed, optimum yields of oil-soluble sulfonic .acids are obtained when the total oleum treat is sufficient to provide 5 to 7 mols of S03 per mol of sulfonatable hydrocarbons in the feed stock. When liquid or `gaseous S03 is used, the ratio is preferably lbetween 2.5 to 3.5 mols of S03 per mol of sulfonatable hydrocarbons. The sulfonating agent may be applied in single or multiple dumps and if multiple dumps are used, sulfonating agents of increasing strength with successive dumps may be used.

The treating temperature during sulfonation is maintained within the range of 32 to 175 F. It is preferred `for convenience to `operate at temperatures in the range of 65 to l00 F. as this requires a minimum of refrigeration.

After the sulfonation, the sludge may be separated from the mixture and sulfonic acid product can be recovered as such or can be neutralized and recovered as oilsoluble sulfonates by conventional means. A preferred processing sequence for working up the products is described in conjunction with the attached schematic illustration which forms a part of this specification.

In a more conventional manner of processing following removal of sulfur dioxide and centrifuging to remove trace pepper sludge, both alkali and alcohol can be simultaneously added to neutralize and extract sodium sulfonate.

The sodium sulfonate can then be further purified. As an alternative, the acid oil can first be extracted as with alcohol to obtain a sulfonic acid concentrate which can then be neutralized with any alkali metal desired. Also, the acids can be neutralized in situ in the diluent oil with such a material as calcium hydroxide to provide for example, a 30% solution of calcium sulfonate in diluent oil.

Suitable solvents include isopropyl alcohol, ethyl alcohol, secondary butyl alcohol, and other alcohols with or without water.

Suitable neutralization agents include alkali metal (Li, Na, K, Rb. Cs) hydroxides and carbonates and alkaline earth (Ba, Sr. Ca. Mg) oxides, hydroxides and carbonates either as solids or in aqueous or alcoholic solutions.

The following description of the attached drawing will serve to make this invention clear. A synthetic alkyl aryl hydrocarbon feed stock, a prepared inert diluent oil and a sulfonating agent, as described above, are supplied to a reaction vessel 4 by lines 1, 2, and 3 respectively. Reaction vessel 4 comprises a conventional high speed type of turbo or shear mixer. The reaction temperature may be maintained by means of heat exchange through the walls of the reactor, by means of cooling coils contained within the reactor, or by means of an external heat exchange with a pumparound system. As mentioned previously, more than one mixing stage with intermitten removal of the sludge may be employed but only one mixing stage is shown for purposes of illustration. The resultant mixture is maintained in reactor 4 for a residence time sufficient to give the desired reaction, usually for a time in the range of 2 to 90 minutes depending on mixing equipment and energy input. The mixture is then passed to a settling zone 5 wherein the sludge which comprises water-soluble sulfonic acids (green acids), SO2, condensation and polymerization products, etc. is separated and removed by line 6. This sludge may be disposed of in a conventional manner as by coking to recover SO2.

It is to be noted at this point that the sludge viscosity of the present process regardless of the amount of acid applied, is unusually fluid. The pepper sludge exhibits completely different behavior from the type of pepper sludge typically obtained in white oil sulfonation. Unusually good separation of this sludge is obtained in the present process. Also, whether the sulfonating agent is applied in a single dump or in multiple dumps, there is no large loss of oil soluble sulfonic acids to the sludge. When the temperature of sulfonation is increased in the Present process, instead of obtaining increasing yields of oil soluble products as is conventional, the oil soluble sulfonic acid concentration in the unreacted oil decreases slightly.

Acid oil comprising the diluent oil, unreacted portions of the feed stock and the desired sul-tonic acids, substantially free from pepper sludge, is withdrawn from settler 5 by line 7 and may be treated as by stripping to remove SO2 as this conserves the amount of neutralization agent that must be used. An oil-immiscible solvent, as above described, is then added by line 8 to the acid oil and the mixture passed to settler 9. The extraction may be carried out in multiple stages if it is desired, usually at a temperature in the range of 32 to 175 F. When using a 50% aqueous solution of isopropyl alcohol, usually l to 3 volumes of alcohol on an absolute basis will be used per volume of sulfonatable hydrocarbons present in the original feed stock.

The oil phase is withdrawn from settler 9 by line 10 and sent to further treating as desired. Such further treating may include further extraction, neutralization, separation and finishing steps.

The lower extract phase containing the sulfonic acids is withdrawn by line 11 and mixed with a neutralizing agent comprising a calcium hydroxide solution containing dissolved calcium chloride which effects a greater lime carrying characteristic to the material and results in a higher neutralization number product. For example, when the extract contains more than 20 weight percent sulfonic acid, it may be neutralized with calcium hydroxide slurry containing 30 to 60 mol percent of calcium chloride and weight percent water, based on the calcium sulfonate product. The mixture passed by line to stripper 15 where the solvent and water are removed. Necessary diluent oil is added by line 14 to meet product requirements. The mixture is then agitated at a temperature of 150 to 200 F. for a period of time generally in the range of 1 to 4 hours to provide the desi-red degree of alkalinity. Following this period of cooking, the temperature is raised to about 300 F. to remove nal traces of water. The stripped material is then passed to lter 18 by line 22, sulfonate product being removed by line 23.

ln the final dehydration of the calcium sulfonate concentrate, obtained as shown in the drawing, the product is usually heated up to about 300 F. to reduce the water content to below about 0.3%. There may be a slight degradation in color and loss of neutralization number because of this cooking. During this dehydration a stream of air may be passed by line 17 through the product to reduce the time required as is conventional but this may -result in further degradation of the calcium sulfonate. To prevent this, an anti-oxidant may be added by line 16 to the materials transferred to the stripper 1S. This antioxidant may comprise such materials as alkylated phenol types and can be added in the amounts of 0.01 to 5%. With the addition of this anti-oxidant, the calcium sulfonate concentrate can be safely dehydrated using air and heat in 15% to 30% of the customary dehydration times.

After passing air supplied by line 17 through the calcium sulfonate concentrate in vessel 15, the dehydrated material can then be filtered such as in a conventional rotary lter to remove solids such as inorganic salts and foreign matter.

EXAMPLE 1 A synthetic alkyl aryl hydrocarbon feed stock comprising polypropylene benzene containing 64 wt. percent of sulfonatable hydrocarbons of 360 to 390 molecular weight was diluted with a prepared inert hydrocarbon diluent oil, which was predominately parainic and had a viscosity of S8 SSU at 100 F. and no snlfonatable hydrocarbons, to yield a combined feed stock containing 30 vol. percent sulfonatable hydrocarbon (46.2 volume percent of feed stock was diluted with 52.8 volume percent of diluent). This feed stock was treated for one hour :at E. at what was determined to be the optimum amount of acid, 6.6 Inols of S03 per mol of sulfonatable hydrocarbon, in a single dump. 24.9 volume percent lof sludge and volume percent of acid oil, based ron combined feed, were obtained upon separation. When the acid oil was neutralized with sodium carbonate and extracted with 50 volume percent isopropyl alcohol, 70.5 volume percent of neutral oil and 25.1 volume percent of soap, based on combined feed, were obtained. The sludge separated from the acid oil had a viscosity of 400 cps. at 40 C. and settled rapidly.

This example shows that according to the invention synthetic feed stocks can be sulfonated to produce a very high yield of sulfonic acids or `soaps of superior color While forming ia relatively small amount of sludge that is easily handled.

EXAMPLE 2 To demonstrate the unexpected eiect of temperature on the sulfonation reaction and on the distribution of sulfonate between the sludge and the acid oil using the acid dosage found to be optimum in a single dump, Table I is presented. The feed stock is the combined feed stock (synthetic feed stock plus diluent oil) described in Example 1. As the treating temperature is increased from 75 F. to 110 F., the yield of oil soluble sulfonate decreases from 25.1 to 23.0 as contrasted to the more typical increase in sulfonate yield customarily experienced in sulfonation of conventional White oil feed stocks. Both acid oil yields and neutral oil yields remained constant in this temperature range. It is believed that higher temperatures increase the amount of dior poly-sulfonates formed.

Table I sULFoNATE YIELD VERSUS TREATING TEMPERATURE To demonstrate the direct neutralization of a concentrate Obtained by the method of this invention as in Example l, a concentrate containing 29 gms. of sulfonic acid per 100 ml. was neutralized with a lime-CaCl2 slurry containing lbs. of lime per gallon of water using sutlicient slurry to obtain 0.273 lb. of lime and 0.0313 lb. CaCl2 per pound of soap. The neutralized concentrate before dehydration contained 22.8 wt. percent calcium sulfonate7 19.3 wt. percent Water and 7.7 wt. percent solids. Following cooking, dehydration and filtration a nal product containing 29.1 wt. percent calcium sulfonate and 0.1 wt. percent water having .a neutralization number of 16.5 was obtained.

Having described the invention, what is sought to be protected by Letters Patent is succinctly set forth in the following clairn-s.

What is claimed is:

1. A process for preparing synthetic alkyl aryl sulfonic :acids having a molecular weight in the range of 400 to 900, which comprises mixing a hydrocarbon feed stock free from hydrocarbons having more than one aromatic nucleus, said feed stock having a sulfonatable hydrocarbon content above 60 volume percent and having as reactive ingredients synthetic alkyl benzene hydrocarbons having 1 to 3 alkyl substituents of such size `that the alkyl portion of the molecule corresponds to a molecular weight in excess of 240 but the entire molecule has a molecular weight no greater than 390, with an inert, sulfuric acid-treated petroleum distillate oil having a sulfonatable hydrocarbon content of less than 0.5%, a boiling range within the limits of 200 to 800 F., and having ra viscosity in the range of 50 to 350 SSU at 100 F., in amounts suicient to obtain a resulting mixture having a sulfonatable hydrocarbon content above volume percent and a viscosity of less than 450 SSU at F., reacting said resulting mixture with a sulfonating agent in amounts suiiicient to provide 2 to 7 mols of S03 per mol of sulfonatable hydrocarbon in said resulting mixture, the reaction being carried out at temperatures in the range of 32 to 175 F. for a time in the range of 2 to 90 minutes, separating sludge from the reaction products, and recovering a `sulfonic acid-containing acid oil.

2. A process for preparing oil-soluble sultonates which comprises mixing a synthetic feed stock having as sulfonatable ingredients :alkyl-substituted aromatic hydrocarbons of l to 2 aromatic rings and 1 to 3 alkyl groups, said aromatic hydrocarbons being capable `of forming sulfonic acid products having molecular weights in the range of 400 to 900, with an inert, sulfuric acid-treated petroleum oil diluent boiling between 200 and 800 F. and substantially free from sulfonatable hydrocarbons to produce a mixture having a sulfonatable hydrocarbon content not below 30 vol. percent and a viscosity of less than 4501 SSU at 100 F., contacting the resulting mixture with sufficient amounts of a sulfonating agent to produce a sulfonic acid concentrate containing 25 to 35% sulfonic acid, separating the reaction products into a sulfonic acid-containing upper oil layer and lower sludge layer, and extracting, neutralizing, and concentrating oil soluble sulfonates from said upper oil layer.

3. A process according to claim 1 wherein said sulfonic acid containing acid oil is admixed with an oil irnmiscible solvent, the resulting sulfonate-containing extract is admixed with a neutralization agent, and the product sulfonates are recovered from the neutralization mixture.

4. A process according to claim 1 wherein said sulfonic acid containing acid oil is admixed with a lime slurry containing a water soluble salt of calcium, and the sulfonate product is recovered from the resulting neutralized oil without extraction.

5. A process according to claim 1 wherein the sulfonatable hydrocarbon is polypropylene-alkylated benzene having a molecular weight of about 360 to 390.

References Cited in the le of this patent UNITED STATES PATENTS 2,456,119 Friedman et al. Dec. 14, 1948 2,573,675 Bloch et al. Nov. 6, 19514 2,616,936 Mammen et al. Nov. 4, 1952 2,635,530 Nevison Oct. 13, 1953 

1. A PROCESS FOR PREPARING SYNTHETIC ALKYL ARYL SULFONIC ACIDS HAVING A MOLECULAR WEIGHT IN THE RANGE OF 400 TO 900, WHICH COMPRISES MIXING A HYDROCARBON FEED STOCK FREE FROM HYDROCARBONS HAVING MORE THAN ONE AROMATIC NUCLEUS, SAID FEED STOCK HAVING A SULFONATABLE HYDROCARBON CONTENT ABOVE 60 VOLUME PERCENT AND HAVING AS RECEIVE INGREDIENTS SYNTHETIC ALKYL BENZENE HYDROCARBONS HAVING 1 TO 3 ALKYL SUBSTITUENTS OF SUCH SIZE THAT THE ALKYL PORTION OF THE MOLECULE CORRESPONDS TO A MOLECULAR WEIGHT IN EXCESS OF 240 BUT THE ENTIRE MOLECULE HAS A MOLECULAR WEIGHT NO GREATER THAN 390, WITH AN INERT, SULFURIC ACID-TREATED PETROLEUM DISTILLATE OIL HAVING A SULFONATABLE HYDROCARBON CONTENT OF LESS THAN 0.5%, A BOILING RANGE WITHIN THE LIMITS OF 200* TO 800*F., AND HAVING A VISCOSITY IN THE RANGE OF 50 TO 350 SSU AT 100* F., IN AMOUNTS SUFFICIENT TO OBTAIN A RESULTING MIXTURE HAVING A SULFONATABLE HYDROCARBON CONTENT ABOVE 30 VOLUME PERCENT AND A VISCOSITY OF LESS THAN 450 SSU AT 100*F., REACTING SAID RESULTING MIXTURE WITH A SULFONATING AGENT IN AMOUNTS SUFFICIENT TO PROVIDE 2 TO 7 MOLS OF SO3 PER MOL OF SULFONATABLE HYDROCARBON IN SIAD RESULTING MIXTURE, THE REACTION BEING CARRIED OUT AT TEMPERATURES IN THE RANGE OF 32* TO 175*F. FOR A TIME IN THE RANGE OF 2 TO 90 MINUTES, SEPARATING SLUDGE FROM THE REACTION PRODUCTS, AND RECOVERING A SULFONIC ACID-CONTAINING ACID OIL. 